The present invention relates to engine control systems, and more particularly to throttle preload verification in displacement on demand engine control systems.
Some internal combustion engines include engine control systems that deactivate cylinders under low load situations. For example, an eight cylinder can be operated using four cylinders. Cylinder deactivation improves fuel economy by reducing pumping losses. To smoothly transition between activated and deactivated modes, the internal combustion engine should produce torque with a minimum of disturbances. Otherwise, the transition will not be transparent to the driver. Excess torque causes engine surge and insufficient torque causes engine sag, both of which degrade the driving experience.
For an eight-cylinder engine, intake manifold pressure is significantly lower during eight-cylinder operation than during four-cylinder operation. During the transition from eight to four cylinders, there is a noticeable torque reduction or sagging in four-cylinder operation until the intake manifold reaches a proper manifold pressure level. In other words, there is less engine torque when cylinders are deactivated than when the cylinders are activated for the same accelerator position. The driver of the vehicle would be required to manually modulate the accelerator to provide compensation for the torque reduction and to smooth torque.
In commonly-owned U.S. Ser. No. 10/150,879 filed May 17, 2002 and entitled xe2x80x9cSpark Retard Control During Cylinder Transitions in a Displacement On Demand Enginexe2x80x9d, which is hereby incorporated by reference, the throttle limit is adjusted to an increased position prior to cylinder deactivation to provide compensation. The increased throttle position or preload is accompanied by spark retard to offset torque increase caused by the preload before the cylinders are deactivated.
An engine control system and method monitors torque increase during cylinder deactivation for a displacement on demand engine. A timer starts at the initiation of cylinder deactivation. A controller communicates with the timer and adjusts the throttle position. The controller further determines whether cylinder deactivation completes within a predetermined time.
In other features, the controller increases throttle position from a normal operating position to an increased operating position when the timer starts. The controller maintains a deactivated throttle position if cylinder deactivation completes within the predetermined time. The controller returns the throttle to the normal operating position if cylinder deactivation exceeds the predetermined time.
A control system and method according to the invention monitors torque increase during cylinder deactivation for a displacement on demand engine. The control system includes a throttle and controller. The controller performs throttle preload and determines if torque increase exists during the throttle preload. The controller cancels the throttle preload if torque increase is detected.
In other features, torque increase is identified when an engine speed derivative exceeds an engine speed threshold, if a sample vehicle acceleration exceeds a vehicle acceleration threshold, if spark advance exceeds a spark advance threshold, and/or if an RPM derivative exceeds a predicted RPM derivative.
A method according to the invention monitors torque increase during cylinder deactivation for a displacement on demand engine. Operating cylinders are deactivated in the displacement on demand engine. Throttle area is increased to the displacement on demand engine from a predetermined area to an increased area. The method determines if cylinder deactivation occurred within a predetermined time. Air delivery is controlled based on cylinder deactivation occurring within the predetermined time by one of; returning to the predetermined area if the cylinder deactivation lasts beyond the predetermined time and maintaining a deactivated throttle area between the predetermined area and the increased area if the cylinder deactivation completes within the predetermined time.
A method for initiating deactivation for cylinders in a displacement on demand engine delivers fuel at a predetermined rate to the displacement on demand engine based on a throttle position. The method determines if a plurality of enable conditions are satisfied. The method performs one of increasing the throttle position and maintaining the throttle position based on the plurality of enable conditions.
In other features, the method further includes maintaining a constant accelerator pedal position. The step of determining includes determining if fuel is shut off to the cylinders of the displacement on demand engine, determining if a higher throttle position is requested and/or determining whether torque increase was detected during a throttle increase event.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.